This invention relates to containers, more particularly to containers for beverages and other pressurized products, and even more particularly to vented containers for beverages and other pressurized products.
Containers with removable closures are often employed for beverages and similar food items. Often containers hold products that are carbonated or otherwise pressurized with a gas For example, carbonated soda or sparkling water includes dissolved carbon dioxide and is bottle at greater than atmospheric pressure. The total pressure within the container is subject to sharply increasing pressure upon an increase in product temperature and upon agitation.
A typical container assembly may include a container, a closure, and (optionally) a liner. The container often has a threaded neck and a top opening. The closure often is substantially cylindrical and includes internal threads that cooperate with the threads on the neck. The liner is disposed inside of the closure above the threads. An interior of the closure and a top portion of the neck urge against the liner to seal the container opening while the closure is in a fully thread position. The container is often formed of a glass or blow-molded plastic, the closure of an injected molded or a compression molded thermoplastic, and the liner of EVA.
Conventional threaded closures employed with carbonated beverages often ineffectively release the internal pressure of the container during opening. For example, upon an initial twist of a conventional closure, the closure and liner move relative to the container body in a screw-like manner. In response to the twisting, the sealing surfaces separate such that the high pressure gases pass through the neck and through the spaced-apart sealing surfaces. The gasses turn direction from substantially upward to substantially downward proximate the inner face of the closure to pass through the threads.
However, because the threads typically present a high pressure drop, the gas pressure only slowly dissipates. Because the closure is partially unscrewed from the container before the pressure dissipates, the pressure urging upward against the closure top and outward against the closure skirt sidewalls may force the closure off the container neck. This phenomenon, which is termed "tail end blow off," may propel the closure from the container and cause injury to persons in the path of the closure projectile. Tail end blow off may occur under high pressure conditions that may be caused by agitation or high temperature of the product common in the usual course of storage and use of the container.
U.S. Pat. No. 4,427,126, entitled "Vented Closure," which is incorporated herein in its entirety, includes vertical grooves formed on the inside surface of the closure that interrupt the threads to promote release of the gas downward through the threads. However, the disclosed closure has several drawbacks. The downward grooves may provide insufficient venting, as evident from its teaching of an extended closure that requires a user to make two turning motions to disengage the closure from the container. The extended closure increases the cost of the closure and inconveniences the user. Further, if a user grips the closure and container neck with his palm, the gases and entrained liquid droplets flowing through the grooves may impinge upon and wet the user's hand.
If is generally difficult simultaneously to provide venting and to maintain tamper resistant measures, including providing indication of an attempt to tamper with the container and its contents.
It is a goal of the present invention to provide a container closure that effectively releases the internal pressure of the container during opening while maintaining tamper-resistance.